Mistakes at a fertility lab at Utrecht’s UMC teaching hospital may mean the wrong sperm was used to fertilise the eggs of 26 different women, the hospital has admitted.

The likelihood this has actually happened is extremely small but cannot be ruled out, the hospital said in a statement.

The mistakes were made between April 2015 and November 2016 and half of the women involved are either pregnant or have given birth. The eggs from the other 13 women have been frozen for future use.

The hospital has informed the couples involved, all of whom will be offered a dna test.

The mistakes happened during a test tube baby technique which involves a sperm cell being directly injected into the egg.

Human error

The problem arose because one of the instruments involved in the treatment was not suitable for the job, the hospital said, adding that this was ‘human error’.

This meant that some sperm from the previous treatment remained in the equipment and could have entered the egg the next time the apparatus was used.

The hospital has since taken steps to ensure the same mistake cannot be made again.